Production of jet fuel



2 Sheets-Sheet 1 Filed May 14, 1959 FIG.I

400-500F. Mid Continent Charge Stock 400E+Producf From Reforming PARAFFINS INVENTO/"P. Paul B. Weisz ATTORNEY Dec. 12, 1961 P. B. WEISZ 3,012,961

PRODUCTION OF JET FUEL Filed May 14, 1959 2 Sheets-Sheet 2 l2 Petroleum 2: Reformmg 2 Charge Stock Zone 0+ 5/ 400 Fruchon Hydrogenation Decalin-Rich Zone Product INVENTOR. Poul B.Weisz ATTORNEY 34112361 PRGDUCTEON F JET FUEL Paul B. Weisz, Media, Pa, assignor to Socony Mobil 051 Company, Inc., a corporation of New York Filed May 14, 1959, ser. No. 813,191 7 Claims. (Cl. 208-66) This invention relates to a catalytic process for manufacturing a saturated dicyclic petroleum hydrocarbon concentrate rich in Decalins. Such material is of interest for various purposes. One important use is as a non-aromatic substantially odorless solvent of relatively low volatility. An especially important application resides in the use as a fuel for jet combustion devices. In particular, the present invention is directed to a method for producing Decalin-rich concentrates by catalytic treatment of selected petroleum fractions.

This invention is particularly concerned with the production of fuels less volatile than gasoline. Such fuels lying in a boiling range generally above that of gasoline are particularly suited for use in continuous combustion engines such as jet propulsion devices of the simple tube or turbo-jet type. These types of engines can be made to operate on a wide variety of fuels including, for instance, kerosene and sometimes low grade gasoline and on higher boiling liquid fuels up to heavy fuel oils but not necessarily at equal or desired operating efficiency. Smooth burning is an important consideration in engines of this type which are often more sensitive to the ignition characteristics of the fuel than the ordinary spark-ignition engines. For maximum combustion efiiciency coupled with high caloric content, freedom from carbon residue, economy of fuel consumption as Well as low volatility and safe flash point to assure freedom from fire and vapor lock hazards in connection with jet fuels, exacting standards and requirements must be met.

For use in turbo-prop and turbo-jet engines, good grades of kerosene have been generally considered accept able except perhaps in cases where lower freezing point requirements prevail but increasing demands for this type of fuel cannot be met by present methods employing catalytic cracking of hydrocarbons except at the expense of distillates required for other uses including motor and aviation gasoline.

From the standpoint of hydrocarbon composition, jet fuels can be distinguished from gasoline by high parafiinicity and low aromatic content. In accordance with usual commercial methods of catalytic cracking, the production of higher yields of aromatics is favored by increased cracking severity resulting in degradation of components desired for jet fuels.

The term jet combustion as generally employed in the art, refers to a method of combustion wherein fuel is continuously introduced into and continuously burned in a confined space for the purpose of deriving power directly from the hot products of combustion. The most complicated forms of jet engines presently proposed consists of a propulsion or jet tube closed at one end plus a gas turbine which extracts sufiicient energy from the departing gases to drive the compressor. In present commercial forms, the compressor and turbine are assembled axially upon a common shaft, spaced far enough apart to permit a number of combustion chambers to be arranged about the shaft between the compressor and turbine, with an exhaust tube extending rearwardly from the turbine. The principal application of such engines is in powering aircraft, particularly for high altitude operations.

Jet combustion filels may boil within a relatively low range of temperature or within a relatively high range of temperature depending upon the particular application. For example, in order to assure quick starting in the operation of military jet propelled aircrafts, jet combus- 3,612,961 Patented Dec. 12, 1961 tion fuels which boil in rather low temperature ranges are used. These fuels, however, have a high A.P.I. gravity and, accordingly, are characterized by less Weight per gallon. The A.P.I. gravity of jet fuels generally increases as the boiling range of the fuel is lowered. As the Weight per gallon together With the number of B.t.u. per unit weight is determinative of the amount of power per gallon of fuel, it is desirable to have the ART. gravity as low as possible.

Another important characteristic of a jet fuel is in the amount of the net heat of combustion, i.e. the number of B.t.u. per pound. This value is ordinarily expressed as the product of the A.P.I. gravity and the aniline number (aniline-gravity product) as described in ASTM Test Methods, D6ll and D-287. As is well known, the aniline-gravity product varies With the number of B.t.u. per pound.

Additional important characteristics of a jet fuel are its storage stability and its sludge-forming tendencies. These characteristics are directly related to the sulfur content, more particularly to the mercaptan sulfur content of the fuel. Accordingly, it is desirable to produce jet fuels that have very low sulfur contents. In the operation of jet combustion devices, deposits of a soot-like character are formed within the combustion chamber and in subsequent portions of the apparatus. These deposits cause operating difliculties by interfering with combustion in the combustion chamber and by damaging the turbine. Soot-forming tendencies of a fuel are measured in terms of the smoke point, i.e. highest flame height in millimeters at which no smoking occurs as measured by the Institute of Petroleum Test No. 57/45.. Accordingly, it is highly desirable for efficient jet engine operation that the smoke point of the fuel be as high as possible.

Further, many jet combustion devices must be operated under low temperature conditions as in Arctic climates or at extremely high altitudes. Under these conditions it is important that the jet fuel remain liquid so that it may be transferred without the use of expensive heating devices. Accordingly, it is desirable for a jet fuel especially the higher boiling fuels, to have the lowest possible freezing point.

The development of supersonic jet aircraft has necessitated cooling of the jet engine. This is accomplished by indirect heat exchange with the incoming jet fuel. Accordingly, the fuel is subjected to temperatures of about 400 to 500 F. which results in the formation of gum and sediment causing the plugging of filters and nozzles, and of lacquer-like deposits in the heat exchange tubes. In order to alleviate this condition, resort has been had to the use of additives but inhibitor response has, in general, not been satisfactory. Furthermore, the development toward ever increasing flight velocities beyond sound velocity leads to frictional heating of the aircraft surfaces. This, in turn, leads to additional pro-heating of the fuels. It is desirable, therefore, to provide a method for the manufacture of jet fuels which exhibit good properties of thermal stability.

In accordance with the present invention, a process has been discovered for the manufacture of jet fuels having the above-desired characteristics, and in particular, the combination of high thermal stability, with high heat content, low smoke-point, and low-freezing point. Broadly stated, the present invention comprises the production of a jet fuel by subjecting a petroleum fraction having an end boiling point of about 500 F. and characterized by components boiling within the approximate range of 400 to 500 F. to a reforming operation in a reforming zone maintained at reforming conditions including the presence of a reforming catalyst, separating the resulting reformate into a fraction boiling below about 400 F. and a fraction boiling above about 400- F. and effecting catalytic hydrogenation of the latter fraction to produce an essentially saturated fuel rich in polycyclic naphthenes. The jet fuel product so obtained is rich in Decalins, low in aromatics, and is characterized by the above noted combination of desired characteristics.

In conventional reforming, it is customary to process petroleum distillate which has a boiling range of approximately 200 to 400 F. to a gasoline product. The distillate materials boiling within the range of 400 to 500 F. lie in a fringe area between gasoline and distillate fuels and have a somewhat indefinite designation as products. A petroleum distillate fraction having an initial boiling point of about 400 F. and an end boiling point of about 500 F. consists of hydrocarbons of carbon numbers ranging approximately from C to C and composed of varying quantities of parafiins, naphthenes and aromatics. For example, a typical Mid-Continent distillate cut boiling within the foregoing range may contain, on a weight basis, 32% parafrlns, 32% monocycloparaiiins, 15% dicycloparaffins, 15% monocycloaromatics and 6% dicycloaromatics.

In accordance with the process of the present invention this type of petroleum fraction is subjected initially to catalytic reforming, followed by separation into fractions boiling respectively below and above 400 F. and subse quent catalytic hydrogenation of the latter fraction to yield a product, having a high content of dicyclic naphthenes, and comprising a jet or rocket propellant fuel of high energy content and thermal stability. The liquid products produced from a 400 to 500 F. boiling range petroleum cut in the process of this invention are quite similar when such fraction is processed either alone, or in conjunction with a lighter portion of a petroleum naphtha, such as a standard range naphtha fraction, as used to obtain gasoline in accordance with conventional reforming operations. Thus, conversion of a petroleum fraction having an initial boiling point of about 400 F. and an end boiling point of about 500 F. may, in accordance with the process described herein, either be carried out alone or practiced simultaneously with reforming of a standard naphtha fraction boiling in the range of 200 to 400 F. Accordingly, it is contemplated that the petroleum fractions, utilized as charge stocks herein, essentially be characterized by an end boiling point of about 500 F. and by the presence of components boiling over the range of 400 to 500 F. Such fractions include those boiling within the approximate range of 400 to 500 F. as well as those boiling over the somewhat broader range of approximately 200 to 500 F.

During reforming of such fractions, components boiling between about 400 F. and about 500 F. undergo the following reactions:

(a) Parafiins in the, original boiling range, having carbon numbers around C to C hydrocrack, with major products (corresponding to. center-cracking) being paraiiins near C to C with a limited amount of cyclization to aromatics, all of the products boiling below 400 F.

(b) Naphthenes (monocyclic) become aromatized (or isomerized-aromatized in the case of S-membered rings) and partly dealkylated, resulting in a portion of material boiling below 400 F.

(c) Alkyl-aromatics present in the charge undergo partial dealkylation resulting in a portion of material boiling below 400 F. v

(d) Polycyclic naphthenes are partly or wholly aromatized, as a result a portion thereof move up in the boiling range above 500 F.

Hydrocracking of paraffins and aromatization of rings during the reforming operation leaves an essentially wholly aromatic residue above the 400 F. boiling point. Moroever, with increasing reforming severity it is anticipated that (a) all alkyl-benzenes undergo conversionto products boiling below about 400 F. (b) all dicyclic materials become fully aromatized to naphthalenes. In the limit of severity, therefore, reforming of 400 500" boiling range hydrocarbon mixtureswould be expected to yield naphthalenes almost exclusively. Approximately 1 /2 fold increase of hydrogen production is observed in the case of reforming of the 400500 F. boiling range petroleum distillate as compared with normal reforming of a petroleum distillate boiling in the range of 200 to 400 F.

A petroleum fraction of the type above described is subjected to catalytic reaction under reforming conditions in the presence of a reforming catalyst. Suitable catalytic composites include compounds of the metals of the left 'hand column of groups V and VI of the periodic table and in particular, the oxides of chromium, molybdenum, tungsten and vanadium, either alone or in admixture with one another and composited with such materials as alumina, magnesia, silica or mixtures thereof. The particular process conditions of time, temperature, pressure and the like employed in any specific operation will vary depending upon the particular catalyst used. The preferred type of catalyst is one comprising a. metal of the platinum group associated with a porous carrier which has slightly acidic properties by virtue of halogen or boron oxide associated with alumina or due to the use as a support of combinations of silica with alumina, magnesia, zirconia, and the like to yield composites characterized by acidic catalytic sites. In particular, it is preferred to employ a catalyst of platinum and alumina. Such catalyst may contain substantial amounts of platinum but for economic as well as for product yield and quality reasons,

the platinum content will usually be within the range of from about .01 percent to about 5 percent by weight. A particularly effective catalyst of this type contains relatively minor proportions usually less than about 5 percent by weight, on a dry alumina basis of a halogen such as chlorine, or fluorine.

It is contemplated that the catalyst employed in the initial reforming step of the instant process may be pre' pared by various procedures well known in the art. As illustrative, one method of preparing a catalyst of alumina and platinum comprises adding a suitable alkaline reagent such as ammonium hydroxide or carbonate to a salt of aluminum such as aluminum chloride, aluminum sulfate, aluminum nitrate, and the like, in an amount sufficient to form aluminum hydroxides which, upon drying, can be converted to alumina. Halogen may be added to the resultant slurry in the form of an acid such as hydro-gen fluoride or hydrogen chloride or as a volatile salt such as ammonium fluoride or ammonium chloride. The fluoride ion appears to be somewhat more active than other members of the halide group and, therefore, 'may be present in a lower concentration than, for example,

when the catalyst contains chlorine. A satisfactory method of adding platium to the alumina-halogen composite comprises preparing a colloidal suspension of platinic sulfide by introducing hydrogen sulfide into an aqueous solution of chloroplatinic acid until said solution reaches a constant color, i.e. until the solution is a dark brown. The resultant colloidal suspension of platinic sulfide is commingled with the aluminum hydroxide slurry at room temperature followed by stirring to obtain intimate mixing. The resulting material is then dried at a temperature 'of from about 200 to about 400 F. for a period of from about 4 to about 24 hours or more to form a cake. The resulting material may then be converted into pellets or other suitably shaped particles. Thereafter, the catalyst is subjected to a high temperature or reduction treatment prior to use. It is to be understood that the foregoing method of preparing satisfactory platinum-alumina catalysts is merely illustrative and is not to be taken in a limitative sense since various other methods may be employed to produce satisfactory catalysts of this type. Other platinum-containing catalysts that may be used in the present process although not necessarily with equivalent results include platinum on charcoal, platinum on silica, platinum-onasbestos, and platinum onbases -or 2) carriers that possess cracking activity such as silicaalumina, silica-magnesia, or silica-zirconia composites. Non-platinum type reforming catalysts may also be used including for example, composites of chromia, and/or stabilizer which effects the separation of the normally gaseous material which comprises hydrogen, hydrogen sulfide, ammonia, and hydrocarbons containing from one to four carbon atoms per molecule, from the normally molybdena with alumina. Such catalysts may be made liquid hydrocarbons. by any of the various procedures known in the art. Thus, The liquid reformate is then in accordance with the a suitable catalytic composite of alumina and chromia present invention, subjected to fractionation to obtain a may be prepared in accordance with the method described fraction boiling above and another fraction boiling below in U.S. 2,773,839 to Stover et al. and a suitable catalyst approximately 400 F. As a result of such fractionation, of alumina, chromia and molybdena may be prepared in there is obtained a liquid boiling below 400 F. which accordance with the method described in US. 2,773,846 constitutes a high octane gasoline or suitable high octane to Stover. blending fraction by virtue of its relatively high content The conditions in the reforming Zone should be such of monocyclic aromatics. There is also obtained a liquid that substantial conversion of naphthenes to aromatics, boiling above 400 F. which is substantially 100 percent relatively mild hydrocracking of paraffins, isomerization aromatic in nature. More particularly, the fraction boilof paraffins, and dehydrocyclization of paraffins are ining above 400 F. may be characterized as follows: duced. Usually the conditions in the reforming zone are, ((7) About 60% of the original 400 F.+ material has a temperature within the range of from about 600 F. been converted to gasoline. to about 1000 F., a pressure of from about 50 to about (0) Remaining 400 F.+ material 'is 98%+ aromatic 1000 pounds per square inch, and a liquid hourly space in nature. velocity of from about 0.1 to about 10. The liquid (0) More than 65% of 400 F.+ product is composed hourly space velocity is defined as the volume of oil per of naphthalenes. hour per volume of catalyst in the reaction zone. It is (0.) Approximately 80% of the 400 F.+ product is preferred that the reforming reactions be conducted in dicyclic in nature. the presence of hydrogen. In one embodiment of the In FIGURE 1 of the attached drawing, a comparison process sulficient hydrogen will be produced in the reacof composition of the 400 F.+ charge material and of tion to furnish the hydrogen required in the process, and, the 400 F.+ product after reforming, for side-by-side therefore, it may be unnecessary to introduce hydrogen comparison, is presented diagrammatically showing the from an external source or to recycle hydrogen Within selective concentration of cyclic and more specifically the process. However, it may be preferred to introduce dicyclic petroleum compositions which takes place. 4 hydrogen from an external source generally at the be- The processing of a petroleum distillate having an end ginning of the operation and to recycle hydrogen within boiling point of about 500 F. and characterized by comthe process in order to be assured of a sulhcient hydrogen ponents boiling Within the approximate range of 400 to atmosphere in the reatcion zone. The hydrogen present 500 F. has been found to give unique results. Thus, a in the reaction zone may be within the range of from lower boiling range fraction does not contain appreciable about 0.5 to about 20 mols of hydrogen per mol of amounts of dicyclic structures, and higher boiling range hydrocarbon. In some cases the gas to be recycled will petroleum cuts when processed do not lead to full aromacontain hydrogen sulfide introduced with the charge or tization of ring structures, nor removal of parafiins. Such liberated by the catalyst and it is within the scope of is illustrated by the data set forth hereinbelow: the present invention to treat the hydrogen-containing Various petroleum fractions boiling in the ranges of gas to remove hydrogen sulfide or other impurities be- 200 to 500 F.; 400 to 500 F.; 500 to 550 F. and 550 fore recycling the hydrogen to the reforming zone. to 600 B, respectively were charged to a reforming zone The effluent from the reforming zone is usually passed at 500 p.s.i.g. total pressure, employing a 10/ 1 hydrogen through a cooler and rnto a separator. In the separator to hydrocarbon mol ratio and a liquid hourly space veloca separation is effe te 0 P o ga e s y l genity of 2 over a commercial reforming catalyst of alumina containing stream and an aromat1c-r1ch hydrocarbon impregnated with about 0.6 weight percent of platinum stream. At least a portion of the hydrogen-rich gas and containing a substantially equal amount of chlorine. stream 1s recycled to the reforming reactor. The aro- Comparisons were madeof charge and product composimatrc-rrch hydrocarbon stream 1s usually passed to a tions. The results are set forth in Table I below:

TABLE I Example 1 2 3 4 5 6 7 8 Y 9 10 11 12 13 14 15 Charge stock boiling range 200-500 200-500 200-500 200-500 200-500 200-500 200-500 200-500 200-500 400-500 400- 00 Reactor inlet temp. F 921 951 970 9 960 950 960 960 91 3 328 1 58 828 328 filii l l l d l ii 72 9 75 4 s1 yie ,vo.percen c .8 80.2 49.1 50. RV? octane No. R+3) 101.0 101.9 101.1 99.8 91.9 94.3 0 parafiins, vol. percent Chg" 0.6 .2 0.4 17.2 21.8 27.0 29.9- 21.8 21.3 20.1 18.7 30.9 192 0 naphthenes,vol percent chg. 5. 5 4. 4 4. 3 2.9 3.2 3. 7 2.3 3. 3 2. 5 2. 3 3. 8 3. 1 6 8 0 aromatics, vol. percent chg 33.8 35.0 40.1 42.2 42.5 45.0 42.4 14.7 -17.1 15.3 9.7 5.8 7 5 0 total, vol. percent chg 70.0 69.6 64.8 02.3 67.5 75.3 74.7 39.8 40.8 37.7 32.1 39.9 3315 400500 F. product:

Parafims, mole percent 2.6 15.6 7.2 6.0 32.9 35,4 3 Naphthenes, mole percent 1.9 1.3 1.2 5. 5 6. 7 11.8 Monccytlic aromatics, mole percen 29.7 28.3 31. 5' 23. Naphthene, mole percent 21.3 22.5 19.2 15% Dicyclic, mole percent 31.4 40.7 42.1 22.6 17.4 12.0 Polycyclic, mole percent 0221 p cenn fl n fln 91.5 92.8 61.4 57.8 51.0

OEYI ,V .per HC 50035.1 i g l t 19 1 1s a 19 2 15 1 12.9

{H3 S, 1110 e percen Naphthenes, mole percent Monocyizzlic aromatics, mole percen Naphthene aromatics, mole 16 8 12 9 21'3 p r e 3.1 2. 0 4.8 Drcyctlrc aromahcs, mole per- CED. Polycyclic aromatics, mole 25.9 124 percent .1 23.1 39.6 24.9 Total aromatlcs, mole percent 100.1 100.0 100.0 Totalyield, vol. percent chm--. 31.9 28.4 37.3

400 F.+ product.

500 F. end-point.

It will be -noted from the foregoing data that a similar extent of conversion of higher boiling materials to gasoline range materials takes place for the various boiling ranges. Also, a similar production of dry gases and butanes occurs in substantially all cases. However, the extent of aromatics production is seen to be drastically decreased when materials of higher than 500 F. boiling range are charged. Such is evident from the lower octane number of the resulting gasoline, its aromatics content, as Well as from the concentration of aromatics produced in the 400 F.+ product. Also, the amount of paraffins remaining in such product, being negligible when derived from the 400 to 500 F. charge stock, increases sharply when the heavier fractions are processed. It is further evident from the above data that operation of the process using the 400 to 500 F. petroleum out alone as the charge stock and the operation wherein this cut is processed simultaneously with the 200 to 400 'F. boiling range fraction lead to qualitatively similar chemical conversions. Thus, in Examples 1 to 9 of the above table, data are set forth concerning the results of reforming of a 200 to 500 F. boiling range fraction and comparisons of these data, in particular the product compositions, with those of Examples 10, 11 and 12 bear out the similarity of the chemical changes which occur when charging the 400 to 500 F. boiling range fraction by itself or with the lighter 200 to 400 F. boiling range material.

Without intending to be limited by any theory, it is believed that the dehydrogenation component of the reforming catalyst, for example the platinum component becomes deactivated with progressive ease as heavier petroleum fractions are charged, thus leaving insufficient activity for aromatization in operation with appreciable quantities of petroleum fractions boiling in excess of about The efiect of optimizing aromatics production bycharging material including the 400 to 500 F. fraction but nothing above this boiling range is felt to be due in part to the relative reaction rates inherent in the chemical compositions of the charge stock, and in part due to a relatively greater catalyst deactivation by the presence of heavier aromatic compounds.

Examples 16-18 A series of reforming runs utilizing a petroleum distillate charge having a boiling range of 200 to 500 F. were carried out at 500 p.s.i.g. pressure, employing a /1 hydrogen to hydrocarbon mole ratio, a liquid hourly space velocity of- 2, a temperature within the range of 910 to 950 F. in the presence of a catalyst of alumina impregnated with about 0.6 weight percent of platinum and con taining a substantially equal amount of chlorine.

The resulting reformates were distilled to determine the product distribution boiling above and below 400 F.

The results are shown in Table II below:

Approximately 21 weight percent of the petroleum distillate change boiled above 400 F. In the products about 13 weight percent (on charge) remain in the boiling range above 400 F. Since product distributionis similar for reforming of a 400 to 500 F. boiling range fraction as well as a 200 to 500 F. boiling'range fraction, it is evident that an appreciable portion of the high-boiling fraction is converted to gasoline range product.

The high concentration of total dicyclic components in the refo'fmate' fraction boiling'above about 400 makes ing the highly naphthalenic products from the described operation through a catalytic hydrogenation zone, thereby converting naphthalenes into Decalin and saturating other aromatic material to naphthenic product. Thus, an essentially completely saturated product of naphthenic character can be produced having some 60% of content in Decalin.

The hydrogenation step of the present process is carried out by contacting the 400 F.+ reformate fraction with a hydrogenation catalyst under suitable hydrogenation conditions. The hydrogenation catalyst may be the same or a different catalyst from that employed in the initial reforming step. Thus, a suitable hydrogenation catalyst is one comprising platinum on alumina containing a minor proportion of halogen. Various other group VIII metals such as nickel, cobalt and iron as well as other metals of. the platinum group deposited on suitable carriers or supports of the type conventionally utilized in hydrogenation catalysts may likewise be employed. Hydrogenation is carried out at thermodynamic hydrogenation conditions, at a temperature within the approximate range of 300 F. to 900 F.; at a pressure between about and about 5000 p.s.i.g., employing a liquid hourly space velocity of between about 0.1 and about 20 in the presence of between about 2500 and about 25,000 standard cubic feet of hydrogen per barrel of charge material. The resulting hydrogenated product possesses a high thermal stability as measured by the CFR Fuel Coker Test described in Appendix 12 of ASTM Standards of Petroleum Products and Lubricants, December 1958. The products so obtained, moreover, afiord a Decalin-rich concentrate characterized by a high heat content, low smoke point, low freezing point and other valuable properties sought in a high quality propellent fuel as will be evident from the following:

Example 19 The hydrogenation charge stock employed was the 400 F.+ fraction from reforming the 400 to 500 F. petroleum distillate fraction under conditions described in Example 12. The charge contained approximately 89 volume percent of aromatics and 71 mol percent of dicyclic aromatics available for conversion to Decalins. Hydrogenation was carried out by passing such charge over a catalyst of alumina impregnated with about 0.6 percent by weight of platinum and containing about 0.7 percent by weight of chlorine at a pressure of 1000 p.s.i.g., an inlet temperature of 500 F, a liquid hourly space velocity of 2 in the presence of 20,000 standard cubic feet of hydrogen per barrel of charge, corresponding to 3.3-3.7 liters of hydrogen per cc. of hydrocarbon charge. The resulting hydrogenated product was collected. The jet fuel characteristics thereof were examined and are set forth in Table III hereinb'elow.

Example 20 Hydrogenation was carried out as described in the previous example except that an inlet hydrogenation temperature of 400 F. was employed. Properties of the resulting hydrogenated product are set forth in Table III.

Example 21 The hydrogenation change stock employed was the 400 F.+ fraction from reforming the 200 to 500 F. petroleum distillate under conditions described in Example 2. The charge stock contained approximately 93 volume percent of aromatics and 73 mol percent of dicyclic aromatics available for conversion to Decalins. Hydrogenation was carired out under the conditions specified in Example 19. The jet fuel characteristics of the resulting hydrogenated product are shown below in Table III.

Example 22 The hydrogenation charge stock employed was the 9 400 F.+ fraction from reforming the 200 to 500 F petroleum distillate described in Example 7. The charge stock contained approximately 100 volume percent of aromatics and 74 mol percent of dicyclic aromatics available for conversion to Decalins. Hydrogenation was carried out under the conditions specified in Example 19. The jet fuel characteristics of the resulting hydrogenated. product are set forth below in Table III.

TABLE III 10 Example 19 20 21 22 Temperature, F.:

Inlet 500 400 500 500 5 Max. bed 671 489 673 701 Liquid product recovery: 1

Vol. percent 119.0 118.8 119.2 118.8 Weight percent 106. 5 106. 5 106. 4 105. 1 H2 consumption, moles/mole HO chg 4.0 4.6 3.4 4.9

COMBUSTION CHARACTERISTICS Heat of combustion:

B.t.u./1b- 18 430 18, 420 18,430 18,360 B.t.u./gal- 130 100 Smoke point, In

PHYSICAL INSPECTIONS CHEMICAL ANALYSIS Sulfur, weight percent Fluorescent Indicator, vol. percent:

Aromatics due to the added hydrogen.

acked gaseous products).

It will be seen from the above data that the heat of combustion of each of the hydrogenated products as indicated by the aniline gravity product, was uniformly high being between 18,300 and 18,400 B.t.u. per pound and between 129,000 to 131,000 B.t.u. per gallon. The smoke points of all products were likewise high being between 22.1 and 23.1 mm. and were substantially better than that of either the 200 to 500 F. boiling range reformate (6 mm.) or pure Decalin (12.4 mm.). The freezing points of all the hydrogenated fuels were below 76 -F. The API gravity and aniline points (F.) were lower with greater naphthenic content fuels. Sulfur contents were extremely low, being less than 0.005 percent by weight for all of the Decalin-rich products.

Suitable means for carrying out the combined reforming, separation and hydrogenation process discussed here in is shown in highly schematic form in FIGURE 2 of the drawing. Referring more particularly to this figure, a petroleum fraction having an end boiling point of about 500 F. and characterized by components boiling within the approximate range of 400 to 500 F. is introduced through line 10 to reforming zone 11 maintained under reforming conditions and containing a suitable reforming catalyst such as platinum deposited on an alumina support. The resulting reformate product is withdrawn from the reforming zone through line 12 and conducted to a fractionation tower 13. A fraction boiling below 400 F. is removed from the fractionation tower through outlet 14 and a fraction boiling above 400 F. is removed through line 15. The latter fraction is conducted through line 15 to hydrogenation zone 16 maintained under hydrogenation conditions described hereinabove and containing a suitable hydrogenation catalyst such as platinum deposited on an alumina support. The desired Decalinrich product is withdrawn from the hydrogenation zone through line 17.

It will be understood that the above-description is merely illustrative of preferred embodiments of the invention, of which many variations may be made within the scope of the following claims by those skilled in the art without departing from the spirit thereof.

I claim:

1. The process which comprises subjecting a petroleum fraction having an end boiling point of about 500 F. and characterized by components boiling within the approximate range of 400 to 500 F. to catalytic reforming, separating the resulting reformate product into a fraction boiling below about 400 F. and a fraction boiling above about 400 F. and catalytically hydrogenating the latter fraction without intermediate treatment thereof to yield an essentially saturated product rich in polycyclic naphthenes.

2. A process for the production of a Decalin-rich concentrate which comprises subjecting a petroleum fraction having an initial boiling point of about 200 F. and an end boiling point of about 500 F. to catalytic reforming, separating the resulting reformate product into a fraction boiling below about 400 F. and a fraction boiling above about 400 F. and catalytically hydrogenating the latter fraction without intermediate treatment thereof to effect essential saturation thereof.

3. A process for the production of a jet fuel which comprises subjecting a petroleum fraction having an initial boiling point of about 400 F. and an end boiling point of about 500 F. to catalytic reforming,separating the resulting reformate product into a fraction boiling below about 400 F. and a fraction boiling above about 400 F. and catalytically hydrogenating the latter fraction without intermediate treatment thereof to yield an essentially saturated product rich in polycyclic naphthenes.

4. A process for the production of a jet fuel which comprises subjecting a petroleum fraction having an end boiling point of about 500 F. and characterized by components boiling within the approximate range of 400 to 500 F. to reforming at a temperature between about 600 F. and about 1000" F., a pressure between about 50 and about 1000 pounds per square inch, a liquid hourly space velocity of between about 0.1 and about 10 and a hydrogen to hydrocarbon mol ratio of 0.5 to 20 in the presence of a reforming catalyst, separating the resulting reformate product into a fraction boiling below about 400 F. and a fraction boiling above about 400 F. and hydrogenating the latter fraction without intermediate treatment thereof at a temperature between about 300 F. and about 900 F., a pressure between about and about 5000 p.s.i.g., a liquid hourly space velocity between about 0.1 and about 20 in the presence of between about 2500 and about 25,000 standard cubic feet of hydrogen per barrel of charge and a hydrogenation catalyst to yield an essentially saturated Decalin-rich product.

5. The process of claim 4 wherein said reforming catalyst and said hydrogenation catalyst consist essentially of platinum impregnated alumina composites.

6. A process for the production of a jet fuel which comprises subjecting a petroleum fraction having an initial boiling point of about 200 F. and an end boiling point of about 500 F. to reforming at a temperature between about 600 F. and about 1000 F., a pressure between about 50 and about 1000 pounds per square inch, a liquid hourly space velocity of between about 0.1 and about 10 and a hydrogen to hydrocarbon mol ratio of 0.5 to 20 in the presence of a reforming catalyst, separating the resulting reformate product into a fraction boiling below about 400 F. and a fraction boiling above about 1 1 1 2 400 F. and hydrogenating the latter fraction without lyst and said hydrogenation catalyst consist essentially of intermediate treatment thereof at a temperature between platinum impregnated alumina composites.

about 300 F. and about 900 F., a pressure between about 100 and about 5000 .p.s.i.g., a liquid hourly space References Cited in the file bf this Patent velocity between about 0.1 and about 20 in the presence 5 I I of between about 2500 and about 25,000 standard cubic p S P STATES PATENTS 1 feet of hydrogen per barrel of charge and ahydrogenation 1,335,596 Marschner Nov. 30, 1943 catalyst to yield an essentially saturated Decalin-rich 2,697,684 Hemminger 31131 1954 product. 2,77 ,215 Hemminger Nov. 27, 1956 7. The process of claim 6 wherein said reforming cata- 10 2,910,426 Glueseflkflmp 6t 31 00L 1959 

1. THE PROCESS WHICH COMPRISES SUBJECTING PETROLEUM FRACTION HAVING AN END BOILING POINT OF ABOUT 500*F. AND CHARACTERIZED BY COMPONENTS BOILING WITHIN THE APPROXIMATE RANGE OF 400 TO 500*F. TO CATALYTIC REFORMING, SEPARATING THE RESULTING REFORMATE PRODUCT INTO A FRACTION BOILING BELOW ABOUT 400*F. AND A FRACTION BOILING ABOVE ABOUT 400*F. AND CATALYTICALLY HYDROGENATING THE LATTER FRACTION WITHOUT INTERMEDIATE TREATMENT 